dispersal of ticks and tick borne diseases by birds - Lista fuglestasjon

The importance of ticks as
disease vectors
Hard ticks (Acari: Ixodidae) have a
significant impact on public health and
the rural economy in many parts of the
world. They are the most important
vectors of infectious diseases to
domestic animals, and they are only
second to mosquitoes as vectors of
diseases to humans (Parola and Raoult,
2001; Jongean and Uilenberg, 2004), see
Box I.
In humans, tick-borne arboviruses cause
neurologic disease and, in some cases,
hemorrhagic fever with high mortality.
The following are of special interest in
Europe: tick-borne encephalitis virus
(TBEV: Western, Far Eastern and
Siberian subtype, i.e., W-TBEV, FE-
TBEV and S-TBEV, respectively),
Louping ill virus (LIV), Omsk
haemorrhagic fever virus, Powassan
virus, Nairovirus, Coltivirus (Eyach
virus) and Crimean-Congo haemorrhagic
fever (CCHF) virus (Charrel et al. 2004).
The serious W-TBE, which is
widespread in Central Europe and the
Baltic countries, has recently been
discovered as causing human infection in
Norway and has also been found in I.
ricinus in Agder, Southern Norway
(Skarpaas et al. 2002 and 2006).
Favourable climatic conditions for
TBEV appear to be present in the coastal
parts of Vestfold, Telemark and Agder
Counties (Randolph and Rogers, 2000,
2001).
Tick-borne Rickettsia fevers (family:
Anaplasmataceae, see Figure 1) of
varying severities are known in many
parts of the world: Rocky Mountain
spotted fever, Boutonneuse fever and
African tick bite fever (Cowan 2003,
Jensenius et al. 2003a and b).
Occasionally, Anaplasma
phagocytophilum may cause serious
disease in humans (Kristiansen et al.,
2001).
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Babesia divergens, which is a cattle disease
may cause disease in humans without a
functioning spleen (Gorenflot et al., 1998)
Lyme disease, caused by bacteria of the
species complex Borrelia burgdorferi s. l., 2
is the most prevalent and widespread vectorborne
human infection in the Northern
Hemisphere and is a main reason for
increased concern about tick-borne
pathogens in this part of the world (de Meeûs
et al. 2002). Before 1995, all cases of Lyme
borreliosis were notifiable in Norway. Since
then, only reporting of cases of chronic and
disseminated Lyme borreliosis has been
mandatory. There has been an increased
incidence of borreliosis in Norway since
1995 (Figure 3). In many other European
countries, an increase of both borreliosis and
TBE was observed between 1990 and 2000
(Randolph, 2001).
In domestic animals, tick-borne diseases
have an immense economic importance
because of increased mortality along with
decreases in milk yields, growth rates,
abortion/calving intervals, hide quality and
the high cost of preventive measures,
including dipping, vaccination,
chemotherapy and veterinary costs (Brown,
1997). Heartwater, caused by Ehrlicia
(Cowdria) ruminatum, may lead to an overall
mortality of about 70% in naïve livestock in
endemic areas (Mahan et al. 2001). East
coast fever (Theileria parva), tropical
theileriosis (T. annulata), babesiosis/redwater
(Babesia bovis, B. major, B. bigemina and B.
divergens) and anaplasmosis (A.
phagocytophilum) are major causes of losses
in cattle (Brown, 1997). Other species of
Anaplasma, Theileria and Babesia attack
sheep (Hashemi-Fesharki, 1997) in tropical
and subtropical regions. In northern Europe,
2 Borrelia is a genus of spirochetes. The
species complex Borrelia burgdorferi sensu
lato comprises all of the Borrelia species
(sometimes referred to as “genospecies”) that
may cause Lyme borreliosis in humans and
also includes species that are
phylogenetically related to the human
pathogenic species (see Figure 2).